NPN Proximity sensor on Duet 6HC

[MaxGyver]

I would like to replace the EdingCNC Controller on my CNC-Router with a Duet 6HC.

The machine is equipped with NPN Proximity endstop sensors (OMRON E28B-S08LS01-MC-C2)
The Mainboard is powered from a 48V power supply and the sensors are powered from a seperate 24V power supply.

I have connected the signal wire (black) to the io0.in pin, (brown) to +24V an (blue) to -24V.
Now in standstill, can confirm that the endstop is triggering correctly when a metal object is placed in front of the sensor by sending M119.

But when I try to home one axis, the matching end stops triggers as soon as the motor moves. Even when I wire the end stop directly in the cabinet with a good distance to the motor wires, the issue persists.
I do not understand how the same configuration works with the old controller but not with the duet.

I am on RRF 3.5-rc.1

; Configuration file for Duet 3 MB 6HC (firmware version 3.3)
; executed by the firmware on start-up
;
; generated by RepRapFirmware Configuration Tool v3.3.16 on Thu Oct 19 2023 17:22:28 GMT+0200 (Mitteleuropäische Sommerzeit)

; General preferences
G90                                     ; send absolute coordinates...
M83                                     ; ...but relative extruder moves
M550 P"CNC"                             ; set printer name

; Network
M552 P0.0.0.0 S1                        ; enable network and acquire dynamic address via DHCP
M586 P0 S1                              ; enable HTTP
M586 P1 S0                              ; disable FTP
M586 P2 S0                              ; disable Telnet

; Device Mode
M453 							; Set device mode to CNC

; Drives
M569 P0.0 S0                            ; physical drive 0.0 goes forwards
M569 P0.1 S1                            ; physical drive 0.1 goes forwards
M569 P0.2 S1                            ; physical drive 0.2 goes forwards
M569 P0.3 S1                            ; physical drive 0.3 goes forwards
M584 X0.0 Y0.1 Z0.2 E0.3                ; set drive mapping
M350 X16 Y16 Z16 E16 I1                 ; configure microstepping with interpolation
M92 X320 Y320 Z160 E420.00              ; set steps per mm
M566 X900.00 Y900.00 Z60.00 E120.00     ; set maximum instantaneous speed changes (mm/min)
M203 X6000.00 Y6000.00 Z180.00 E1200.00 ; set maximum speeds (mm/min)
M201 X500.00 Y500.00 Z20.00 E250.00     ; set accelerations (mm/s^2)
M906 X2000 Y4200 Z4200 E800 I30         ; set motor currents (mA) and motor idle factor in per cent
M84 S30                                 ; Set idle timeout


; Axis Limits
M208 X0 Y0 Z0 S1                        ; set axis minima
M208 X1010 Y1245 Z200 S0                ; set axis maxima

; Endstops
M574 X1 S1 P"io0.in"                    ; configure switch-type (e.g. microswitch) endstop for low end on X via pin io0.in
M574 Y2 S1 P"io1.in"                    ; configure switch-type (e.g. microswitch) endstop for high end on Y via pin io1.in
M574 Z1 S1 P"io3.in"                    ; configure switch-type (e.g. microswitch) endstop for low end on Z via pin io3.in

; Z-Probe
M558 P0 H5 F120 T6000                   ; disable Z probe but set dive height, probe speed and travel speed
M557 X15:215 Y15:195 S20                ; define mesh grid


; Sensors
M308 S4 Y"drivers" A"DRIVERS" ; configure driver temperature sensor
; Heaters

; Fans

; Tools
M563 P0 D0 F0                           ; define tool 0
G10 P0 X0 Y0 Z0                         ; set tool 0 axis offsets
G10 P0 R0 S0                            ; set initial tool 0 active and standby temperatures to 0C

; Custom settings are not defined

[MaxGyver]

@dc42 Thank you for your feedback.

Inverting the input was the first thing I tried without success.

In this case I did not design or build the control cabinet, I can only recon that the 48V and 24V PSU do not share a common ground and therefore the end stops behave strange.

When powering the duet and endstops from the same 24V PSU everything works as intended.

[dc42]

@MaxGyver if it's a normally open NPN sensor then you need to tell RRF to invert the input so that a low voltage indicates that the endstop is triggered. Do this by using "!io0.in" instead of "io0.in" in the M574 command.

[MaxGyver]

@dc42 Thank you for your feedback.

Inverting the input was the first thing I tried without success.

In this case I did not design or build the control cabinet, I can only recon that the 48V and 24V PSU do not share a common ground and therefore the end stops behave strange.

When powering the duet and endstops from the same 24V PSU everything works as intended.